For managing multiple client accounts ISP (static residential proxies) are the best.
Services that artificially increase watch hours typically rely on large bot networks, compromised devices, residential/mobile proxy pools, or paid click farms combined with automated viewing to mimic real users. The exact infrastructure varies, but it's designed to evade platform detection and violates most platforms' terms of service.
The proxy type is only one piece of the puzzle. Different providers use different infrastructure, but there isn't a single proxy type that guarantees success. In general, residential and mobile IPs tend to resemble normal user traffic more closely than datacenter IPs, but account quality, viewing patterns, and overall behavior usually have a much bigger impact than the proxy itself. If your goal is legitimate account management rather than artificially inflating metrics, I'd focus on a stable, consistent setup instead of chasing a specific proxy type.
selecting an apropriate proxy is not the only part of the configuration proces. In my opinion, platform usualy give preference to the behavior of trafic rather than the exact kind of IP that is utilized.
Beyond proxies, I suspect they’re also using automation or tools to manage large numbers of accounts; as for the proxies themselves, they’re likely using ISP or residential proxies.
